The present invention relates to a micro-hard disk drive system, and in particular, a micro-Winchester high capacity disk drive in which the read/write heads are used to generate and protect a hard sectoring scheme.
With the rapidly expanding development of personal computers, portable personal computers and desk top data processing systems, there has been a demand for increasing the performance of the disk drive systems of such computers. A major development in that direction has been the introduction of small Winchester disk drives as replacements and enhancements to floppy disk drives for program storage. The Winchester disk drive in general provides higher capacities and faster speeds of operation, factors which are important for the effective use of personal computers running advanced software packages.
The types of Winchester disk drives that have been developed in that regard were based upon the use of hard disks of diameter of approximately five and one-quarter inches, also known as mini-Winchester disks. Such so called "five and one-quarter inch" disk drives have generally developed as an "industry standard." Such Winchester disk drive systems can typically store 5-30 Megabytes of information when designed around an open-loop positioning system using a stepper motor capable of supporting up to approximately 360 data tracks per inch. However, advances made by the assignee of the present invention have expanded the storage capacity of the typical five and one-quarter inch disk drive up to 600 tracks per inch using the same basic type of open-loop postioning system. Such a track density had previously been believed unobtainable with stepper motor technology.
With the introduction of portable personal computers, it is clearly a performance advantage to achieve a high degree of software compatibility with the desk top computing systems. In addition, portability demands special requirements on the incorporation of a hard disk system, for example, light weight, low-power consumption and the capability of withstanding harsher shock and vibration conditions. However, software compatibility also demands performance parameters, such as data storage capability comparable to those available on five and one-quarter inch mini-Winchester disk drive systems.
Among the various advances that have been made in the construction and operation of disk drive systems are those developments made by the assignee of the present application, Rodime PLC, which developments are set forth in the following U.S. Patent and Patent applications. The subject matter of such patent and patent applications is hereby incorporated by reference.
U.S. Pat. No. 4,392,095, entitled "Method of and Apparatus for Generating a Unique Index Mark from the Commutation Signal of a D.C. Brushless Motor," discloses a system for providing a unique index mark relative to the computer disk which is required for avoiding errors in addressing a memory location on the disk surface. That index mark is provided by correlating the commutation signal from a d.c. motor with a synchronizing signal present on one or more discrete tracks of the computer disk.
U.S. Pat. Application Ser. No. 332,003, entitled "Read/Write Head Thermal Compensation System," discloses a thermal compensation system used by Rodime PLC in its five and one-quarter inch disk drive system. That thermal compensation system uses different materials with different coefficients of thermal expansion for various components of the positioning mechanism for the read/write head used in the disk drive system. In the operation of that thermal compensation system, in response to a change in temperature, a mispositioning of the read/write head is compensated for by a counter-movement due to the selection of various materials with different coefficients of thermal expansion within the mechanical arrangement.
U.S. Pat. No. 4,538,192, entitled "Ventiliation System for a Computer Disk Drive Hub Assembly," discloses a ventilation system for use in a computer disk drive which enables the disk file data storage capacity to be increased for a given volume of chamber housing the disk and improves the disk drive operating performance.
U.S. Pat. No. 4,489,259, entitled "Method and Apparatus for Controlling a Stepper Motor," discloses a system for minimizing oscillations of the stepper motor for a single step, minimizing the time taken for the stepper motor to move between tracks for multi-track seek operations and reducing the angular hysteresis due to the mechanical and magnetic properties of the stepper motor construction. In controlling the operation of the stepper motor, a microprocessor circuit is adapted to drive the stepper motor in accordance with predetermined programs.
U.S. Pat. No. 4,568,988, entitled "Micro-Hard Disk Drive System," discloses a high-density micro-Winchester hard disk system using a hard disk of approximately three and one-half inches and having digital information stored at a density of approximately 600 concentric tracks per inch, and at a storage density equivalent to at least 5 Megabytes per hard-disk. A stepper motor is designed to increment in steps of 0.9.degree. which causes the read/write head to move from one track to the next adjacent track on the hard disk. For many applications, it has now become advantageous to utilize a high performance three and one-half inch Winchester disk drive having a storage capacity in excess of that achieved in the above-disclosed micro-hard disk drive system, namely in excess of 10 Megabytes. Such increased storage capacity allows the use of more sophisticated programs and the storage of data for use therewith than has been possible heretofore.
Such prior art disk drives have almost exclusively used the "industry standard" ST 506 interface to the host system. That interface has the disadvantage that it defines fundamental operating parameters of the disk drive, such as MFM (modified frequency modulation) coding, data transfer rate and disk rotational speed, which limit the storage capability of the disk drive.
Although the invention described herein utilizes an open-loop positioning system to achieve cost effectiveness while still attaining a storage capacity in excess of 10 Megabytes, a more expensive closed-loop positioning system could readily be utilized in place of that open-loop positioning system.
Most hard-disk drive systems utilize a system which provides one reference mark or index pulse per revolution so that the user can format each track on the drive into a plurality of sectors. Each of those sectors includes a header which contains information which identifies the sector and track location. That information is read by the drive every time data is read from or written to that sector. Such a scheme of operation is called soft-sectoring. However, soft-sectoring has the disadvantages that it is difficult to implement, requires more hardware and is more expensive than hard-sectoring.
Hard-sectoring, in which the disk drive physically provides a mark for every sector pulse as well as once per revolution of the disk, is less complex and less expensive than soft-sectoring and is desirable for connection to certain computers which may already be designed to use such hard-sectoring techniques.
In prior art systems, the necessary sector and index pulses were produced by means of a transducer and some form of code wheel which was rotated by the drive motor. Typically, such transducers were either optical or electromagnetic. They sensed the revolving wheel and generated a pulse for every sector mark. However, such prior art hard-sectoring systems, although requiring less hardware than soft-sectoring schemes, still require hardware over and above that necessary to operate the drive. In addition, such hard-sectoring systems require alignment of the transducer with the code wheel, and the maintenance of that alignment under operating conditions.